The present invention relates to a fluid based cleaning method and system, particularly for the cleaning of garments, fabrics, substrates, complex materials or the like, but also for sterilizing purposes. More specifically, the invention relates to the supplying of a cleaning fluid, particularly liquid carbon dioxide, pure or with additives, to a customer application system of said cleaning system.
Conventional dry-cleaning devices use solvents, which are risky as regards health and safety, and environmentally detrimental. For example, perchlorethylene is possibly carcinogen, while petroleum based solvents are flammable and produce smog.
Liquid carbon dioxide has been proposed as a dry-cleaning fluid, see, e.g., U.S. Pat. No. 5,784,905 and U.S. Pat. No. 5,683,473 issued to Townsend al. and to Jureller et al., respectively, and references therein.
Liquid carbon dioxide has many attractive properties for use as a dry-cleaning medium; it is an inexpensive and unlimited natural resource, that is non-toxic, nonflammable, and does not produce smog, or deplete the ozone layer. It does not damage fabrics or dissolve common dyes, and exhibits solvating properties typical of hydrocarbon solvents.
A typical liquid carbon dioxide based dry cleaning system includes a confined high-pressure chamber for containing liquid carbon dioxide in liquid phase, at typical process temperatures of about 0.degree. to 30.degree. C., and at typical pressures of 35 to 70 bar. A high-pressure tank or reservoir is provided for supplying liquid carbon dioxide to the confined chamber. The carbon dioxide solvent may contain various additives, such as surfactants, antistatic agents, fragrance and deodorizing agents. The confined chamber may include a basket or a drum to hold the objects to be cleaned. There may be provided an agitation means or some other means for agitate or move the liquid carbon dioxide relative to the objects. Example of such a liquid carbon dioxide dry cleaning system is discussed in said U.S. Patents and in U.S. Pat. No. 5,467,492 issued to Chao et al.
When using such a cleaning system the solvent is "consumed", i.e., and, even though the solvent to some extent may be decontaminated through filtering, it will finally become useless and has then to be purified, e.g., through distillation.
A problem with this kind of dry-cleaning system is that non-avoidable losses of carbon dioxide to the atmosphere arises as a consequence of opening the cleaning chamber for loading and unloading of objects. Also, other types of losses occur during operation, e.g., due to venting of non-condensed carbon dioxide to the atmosphere. These losses are troublesome, as the dry-cleaning device needs a certain amount of carbon dioxide to operate properly.
Prior art liquid carbon dioxide dry-cleaning systems solves this by dimension the high-pressure tank or reservoir so that there is enough carbon dioxide for a predetermined number of cycles. Then carbon dioxide has to be supplied to the dry-cleaner. This is generally performed at regular time intervals, e.g., every second week, by delivery of carbon dioxide from a mobile tank, e.g., a tank lorry.
A problem, here, is that the tank/reservoir gets very large, and as a result the dry-cleaner becomes bulky and as a consequence, difficult to place.
Very compact dry cleaners, where restrictions are put on the size of the tank/reservoir, would need delivery of carbon dioxide very frequently; or would otherwise suffer from malfunction due to lack of carbon dioxide.
Another problem is that the pressure in the tank/reservoir is higher than the most common pressure in tanks for distribution of carbon dioxide or carbon dioxide based products. A higher pressure, sufficient for filling the tank/reservoir, could be achieved by, for example, using a high-pressure delivery tank, which, however, will be heavy and reduce the capacity of the truck for other goods.
An alternative is to use a pump installed either at the delivery tank, which will be costly, noisy and hard to operate, particularly when a small distrbution tank is used, or at the customer place (dry-cleaner system) and connected to a low pressure tank to which the liquid from the delivery tank is filled, which will be costly because a pump is needed, and also higher maintenance costs are expected.